xgettext: Signal a warning when the same msgid is used with and without plural.
* gettext-tools/src/xg-message.h (remember_a_message): Add pluralp argument.
* gettext-tools/src/xg-message.c (remember_a_message): Likewise. Signal a
warning when the same msgid is used with and without plural.
* gettext-tools/src/xg-arglist-parser.c (arglist_parser_done): Update
remember_a_message invocation.
* gettext-tools/src/xgettext.c (xgettext_its_extract_callback): Update
remember_a_message invocations.
* gettext-tools/src/x-awk.c (extract_parenthesized): Likewise.
* gettext-tools/src/x-c.c (extract_parenthesized): Likewise.
* gettext-tools/src/x-csharp.c (extract_parenthesized): Likewise.
* gettext-tools/src/x-desktop.c (extract_desktop_handle_pair): Likewise.
* gettext-tools/src/x-elisp.c (read_object): Likewise.
* gettext-tools/src/x-java.c (extract_parenthesized): Likewise.
* gettext-tools/src/x-javascript.c (extract_balanced): Likewise.
* gettext-tools/src/x-librep.c (read_object): Likewise.
* gettext-tools/src/x-lisp.c (read_object): Likewise.
* gettext-tools/src/x-lua.c (extract_balanced): Likewise.
* gettext-tools/src/x-perl.c (extract_variable, interpolate_keywords,
extract_balanced): Likewise.
* gettext-tools/src/x-php.c (extract_balanced): Likewise.
* gettext-tools/src/x-python.c (extract_balanced): Likewise.
* gettext-tools/src/x-rst.c (extract_rst, extract_rsj): Likewise.
* gettext-tools/src/x-scheme.c (read_object): Likewise.
* gettext-tools/src/x-sh.c (read_word, read_command): Likewise.
* gettext-tools/src/x-tcl.c (read_command): Likewise.
* gettext-tools/src/x-vala.c (extract_balanced): Likewise.
* gettext-tools/src/x-smalltalk.c (phase3_pushback, phase3_pushback_length): New
variables.
(phase3_get): Renamed from x_smalltalk_lex. Handle pushback.
(phase3_unget): New function.
(extract_smalltalk): Update remember_a_message invocations through a lookahead
of one token.
* gettext-tools/src/x-ycp.c (phase8_pushback, phase8_pushback_length): New
variables.
(phase8_get): Handle pushback.
(phase8_unget): New function.
(extract_parenthesized): Update remember_a_message invocations through a
lookahead of one token.
* gettext-tools/tests/xgettext-15: New file.
* gettext-tools/tests/Makefile.am (TESTS): Add it.
